Re: vt220 default for serial console still relevant?

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Nevermind that, I just forgot to remove my override file that set TERM=linux for serial-getty@ttyS0.

Daan

On Sat, 11 Jul 2020 at 20:31, Daan De Meyer <daan.j.demeyer@xxxxxxxxx> wrote:
> TERM=linux means Linux console, but that's just too much, as it not
> only implies a multitude of ESC sequences specific to the Linux
> console, but also indicates that certain ioctls might work. In our own
> code we also bind certain behaviour to TERM=linux, as indicator if we
> are on the Linux console.
>
> I am not aware of any widely-supported TERM value that would be a
> reasonable subset of all currently used terminals and does color.

I did some more research and it turns out VT220 does support colors. My terminal emulator (Konsole) just doesn't seem to support it. I installed xterm (which explicitly advertises support for VT220 escape codes) and got colored output as expected.  I guess this means it's up to Konsole to support more of VT220 if I want this to work seamlessly (or I switch terminals to xterm).

Thanks for the extra info and context.

Daan

On Sat, 11 Jul 2020 at 20:04, Lennart Poettering <lennart@xxxxxxxxxxxxxx> wrote:
On Sa, 11.07.20 17:51, Daan De Meyer (daan.j.demeyer@xxxxxxxxx) wrote:

> Hi,
>
> I was playing around with mkosi's qemu support, more specifically adding
> the -nographic option to have the virtual machine output in my terminal
> instead of a separate window. After figuring out that I had to add
> console=ttyS0 to mkosi's kernel command line, I got the output from the vm
> in my terminal as expected. However, because systemd defaults to TERM=vt220
> for serial consoles, the output is not colorized. I searched around a bit
> and found that this is done for compatibility reasons. Will there ever be a
> point where we can switch the default to something that supports colors
> (like TERM=linux)?

TERM=linux means Linux console, but that's just too much, as it not
only implies a multitude of ESC sequences specific to the Linux
console, but also indicates that certain ioctls might work. In our own
code we also bind certain behaviour to TERM=linux, as indicator if we
are on the Linux console.

I am not aware of any widely-supported TERM value that would be a
reasonable subset of all currently used terminals and does color.

> I managed to get around the problem by overriding serial-getty@ttyS0 and
> setting Environment=TERM=linux explicitly but it's a bit of a pain and has
> to be added to every rootfs that wants to support colored output on its
> serial console.

Unfortunately we can't guess the right terminal, we cannot propagate
TERM=xterm or TERM=linux depending if you invoke qemu on an xterm or
from a Linux console, hence the best thing we can do is stick to a
reasonably powerful subset that is likely going to exist everywhere,
and that's vt220 right now, as noone had a better suggestion so far...

Lennart

--
Lennart Poettering, Berlin
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